1. Field of the Invention
This invention relates to light distribution control of a head lamp device for changing a lighting region in right and left directions.
2. Discussion of Relevant Art
Hitherto, various head lamp devices capable of changing a lighting region in right and left directions have been proposed. In almost of all of them, basically the lighting region of a head lamp is controlled to change in response to a steering angle of the steering wheel (Japanese Laid-Open Patent Publications No. Sho 62-77249, No. Hei 3-14742 etc.) and the lighting region of the head lamp is changed to a direction of the steering operation to increase a lighting amount in the direction to which the vehicle is just going to advance.
If the lighting angle is controlled in response to the steering angle only as above, when the steering operation is rapid, the lighting angle is also changed rapidly in response to rapid change of the steering angle so that the lighting region is swung in right and left directions and largely in a moment to give the driver a sense of incongruity.
When a vehicle goes around a curve, for example, if the steering wheel is turned through too large an angle as compared with the vehicle speed, or the road surface is in a slippery state such as a snowy road, sometimes the rear part of the vehicle projects outwardly such that it directs the vehicle inward too much. FIG. 8 shows such a state in which a vehicle 02 shown by the solid line is directed inward too much on a midway of a road curving to the right.
In such a case, if the steering wheel is left in the state turned to the right, the vehicle 02 turns round, however by reversing the turning direction of the steering wheel (counter-steering) the direction of the vehicle body can be recovered. In FIG. 8, therefore the steering wheel is turned to the left by counter-steering so that the front wheels 03 are directed leftward with respect to the vehicle body.
If the lighting region of the vehicle 02 is changed in response to the steering angle, before the steering wheel is reversed to the left direction, the region on the right side with respect to the front of the vehicle body is lighted as shown by the dotted line 04 in FIG. 8, and after the counter-steering, the lighting region is directed to the left side with respect to the front of the vehicle body as shown by the solid line 05.
As the counter-steering is carried out instantaneously, the lighting region is changed instantaneously from the region 04 to the region 05, and the rapid and large change of the lighting region gives the driver a sense of incongruity.